The present invention relates to refractory shapes and particularly bricks suitable for use in kiln operations utilizing lime rich clinker, more specifically, rotary lime and cement kilns.
Because of their excellent strength and resistance to spalling magnesite-chrome refractory shapes such as brick were extensively used in the rotary kiln industry. However, with knowledge that the chrome in such brick reacted with alkali in the kiln to form hexavalent chrome, a potentially hazardous material, the use of such type of brick has been greatly diminished. The reason for this is that as a potentially hazardous material it has to be disposed of accordingly which places a large additional cost on operators of such kilns.
Efforts to substitute other materials such as magnesite-spinel brick for this purpose have increased but such brick do not give a performance up to that o obtainable with the magnesite-chrome compositions. For example, the magnesite-spinel brick have a high thermal conductivity, as well as poor thermal spalling resistance particularly when used in vessels handling lime-rich clinkers. While some improvement in lowering thermal conductivity has been obtained, efforts to improve thermal spall resistance to a more satisfactory level has not occurred.